1. Field of the Invention
The present invention relates to an electrophotographic copying machine having a flash lamp for illuminating a document to be copied.
2. Description of the Prior Art
There is known an electrophotographic copying machine having a flash lamp for producing a flash of light to illuminate a document to be copied. The optical image of the illuminated document is focused onto a photosensitive body to form an electrostatic latent image thereon, which is thereafter developed into a visible image by an image developing device.
The flash lamp in such a copying machine may not be energized due to a malfunction, a failure, or a life termination of itself and/or a power supply circuit for the flash lamp. Since the flash lamp emits light through an electric discharge produced between electrodes, the flash lamp cannot be checked for a malfunction or a failure by way of a visual inspection which would be effective for a tungsten lamp, for example, having a tungsten filament which is heated for light emission. Furthermore, it is impossible for the operator to ascertain, from outside of the copying machine, whether light is being emitted from the flash lamp or not, because the copying machine is constructed not to allow light to leak out of the machine. Even when the operator finds the flash lamp inoperative during operation of the copying machine, several tens of copies that are fully black with toner will have been produced by that time because the copying machine with the flash lamp operates at high speed. Such fully black copies are problematic in that they are wasteful of toner and image transfer sheets, the toner is scattered around in the machine, and an image transfer sheet fully blackened with toner tends to be wound around an image fixing roller, causing a paper jam in the machine.
In conventional copying machines with flash lamps, a copy counter is not corrected when the flash lamp fails to be energized during machine operation. When the flash lamp is not energized during machine operation, the produced copy is fully blackened with toner and hence is not useful as a normal copy, but the copy counter counts it as a normal copy.
Some copying machines with a collating capability can copy a plurality of pages from each of a plurality of documents, sort and staple the copies into a plurality of sets of copies. Failure of the flash lamp in such a copying machine results in other drawbacks. For example, those copies which are fully black with toner have to be subsequently located and removed, and proper copies have to be produced again from corresponding pages and inserted into their positions in the proper sequence. Where many sets of copies are to be produced, the operator is required to find, if any, which set(s) and page(s) contain wrong copies resulting from a flash lamp failure.